Carbon dioxide analyzer cartridge assembly



June 4, 1963 w. M. RAND, JR., ETAL 3,092,466

CARBON DIOXIDE ANALYZER CARTRIDGE ASSEMBLY Original Filed Nov. 10, 19585 Sheets-Sheet 1 June 4, 1963 w. M. RAND, JR., ET AL 3,092,466 CARBONDIOXIDE ANALYZER CARTRIDGE ASSEMBLY Original Filed Nov. 10, 1958 5Sheets-Sheet 2 June 4, 1963 r Fig.5

W. M. RAND, JR., ETAL CARBON DIOXIDE ANALYZER CARTRIDGE ASSEMBLYOriginal Filed Nov. 10, 1958 5 Sheets-Sheet 3 June 4, 1963 w. M. RAND,JR., ETAL 3,

CARBON DIOXIDE ANALYZER CARTRIDGE ASSEMBLY Original Filed Nov. 10, 19585 Sheets-Sheet 4 June 4, 1963 w. M. RAND, JR., ETAL 3,092,466

CARBON DIOXIDE ANALYZER CARTRIDGE ASSEMBLY Original Filed Nov. 10, 19585 Sheets-Sheet 5 United States Patent 3,092,466 CARBON D NEH- ANALYZERCARTRIDGE ASSEMBLY William M. Rand, .lr., Lincoln, Richard E. Rice,Arlington, Robert G. Shaver, Concord, and Wiiliam E. Whitney, Belmont,Mass., assignors to Comstock & Westcott, Inc., Cambridge, Mass, acorporation of Massachusetts Original application Nov. 10, 1958, Ser.No. 772,910, now Patent No. 2,035,903, dated May 22, 1962. Divided andthis application Nov. 12, 1959, Ser. No. 855,486 2 Claims. (Cl. 23-455)This invention relates to an improved method of determining the amountof carbon dioxide in a gas stream of an anesthesia system of theclosed-circuit type, and in particular it relates to a novel apparatuswhich makes such a determination.

Industry has been confronted with a three-fold problem in their attemptto solve the difiiculties of the anesthesiologist in his appraisal ofthe amount of carbon dioxide in the anesthesia system. First, arepresentative sample of the anesthesia gas stream must be acquired;second, the sample must be automatically analyzed for carbon dioxidequickly and accurately; third, the method of analysis must have utilityin an operating room, the atmosphere of which may contain gaseousexplosive components.

We have invented an apparatus which will determine the amount of carbondioxide in the anesthetic gas stream of a closed-circuit rebreathingsystem, and not only will the determination be made accurately andquickly but also the apparatus may be manually activated into operationby one hand of the anesthesiologist. The accuracy of the presentapparatus is about plus or minus 0.20% when the carbon dioxide contentof the anesthesia stream is present in an amount up to about by volume.This accuracy is not only unaffected by the presence of anesthesticconcentrations of the conventional gaseous anesthetics such as nitrousoxide, cyclopropane, ether and the like, but also the accuracy isunafiected by the inherent differential pressure due to exchange ofmoisture between the stream and the absorbent because the stream ishumidifiably conditioned prior to contact with the absorbent to nullifythis effect. Also of importance is the fact that the apparatus iscompact, light in weight, is constructed so that no static chargebuild-up will take place and does not depend upon electricity for itsoperation which makes it acceptable for use in the operating room.

In general, the process of the present invention comprises capturing asample of gas from the anesthesia stream which is circulating in arebreathing system of the closed-circuit type, contacting such samplewith a humidifying agent which standardizes the moisture content of thesample, adjusting the pressure of the sample to substantiallyatmospheric pressure and treating a known volume of such standardizedsample with an absorbent which preferentially extracts the volume ofcarbon dioxide present producing a pressure change in the standardizedsample which is proportional to the carbon dioxide extracted, andmeasuring the pressure change produced by the said extraction.

More particularly, in the process of the present invention arepresentative sample of gas from an anesthesia stream, which iscirculating in a rebreathing system of the closed-circuit type, andwhich contains carbon dioxide in an amount up to about 15% by volume, iscaptured. This representative sample is treated with an ammonium sulfatehumidity conditioning agent whose function it is to standardize thehumidity of the sample to substantially the same humidity as is inequilibrium with the carbon dioxide absorbent hereinafter described.

3,092,466 Patented June 4, 1963 The pressure of the sample is adjustedto substantially atmospheric pressure, and a known volume of said sampleis contacted with a soda lime absorbent which preferentially extractsthe carbon dioxide present in the sample producing a partial vacuum witha correlating decrease in the internal pressure of the sample which ismeasuneable.

In theory, any humidity conditioning agent which if contacted with thegas sample would provide a humidity that is constant at a giventemperature and which also corresponds to the humidity of the carbondioxide absorbent, hereinafter described, is applicable in the presentprocess. The humidity conditioning agent which has been preferentiallyutilized in the present process is a saturated aqueous solution ofammonium sulfate imbibed on ammonium sulfate crystals or granules.Ammonium sulfate has the advantage of being a cheap, readily available,crystalline salt that is relatively noncorrosive and non-toxic.

The concentration of the saturated solution of ammonium sulfate which isdeposited on the ammonium sulfate crystals or granules, is such that itwill bring the relative humidity of the anesthesia gas with which it iscontacted to between about 70% and about 90% relative humidity when themoisture content of the absorbent is between about 20% down ot about10%. Preferentially this humidifying agent should bring the moisturecontent of the treated anesthesia gas stream to a relative humidity ofabout 85% when the moisture content of the absorbent is about 15Although many known absorbents may be utilized in the present process wehave preferably utilized soda lime as the carbon dioxide absorbent. Thecharacter of soda lime is such that while it has little aflinity fororganic, neutral, non-polar gases which are present in the anesthesiagas stream, however, it does have a strong afiinity for carbon dioxide,which is anacidic-type gas. Soda lime, because of its preferentialabsorption character has a greater preformance reliability in anesthesiasystems which are made up of varying components at ordinary roomtemperature.

It has been found that soda lime, which has a moisture conetent betweenabout 10% and about 20%, may be utilized in the present process. If themoisture content is less than about 10% or more than about 20% there isa tendency for the soda lime to become ineffectual in absorbing carbondioxide. Satisfactory absorptive characteristics were obtained when themoisture content of the soda lime is between about 14% and about 19%,with the optimum desirable carbon dioxide absorptivi-ty being achievedwhen the moisture content of the soda lime was about 15%. It has beenfound that soda lime with a moisture content of about 15% will not addmoisture to, nor subtract from, a gas which has a relative humidity ofabout It is the function of the aforedescribed ammonium sulfatehumidifying agent to preferably bring the captured sample, whichcontains carbon dioxide, to approximately this humidity.

As a result of the extraction of carbon dioxide from the gaseous samplea partial vacuum is produced therein which is not only measurable but isalso directly correlatable to the amount of carbon dioxide extractedthere from. It has been found that this measurement may be made with ahigh degree of accuracy by a number of conventional means, because anyinherent error due to an inherent loss or gain in pressure resultingfrom the transfer of water vapor between the sample and the carbondioxide absorbent, is nullified because the humidity of the gas has beenstandardized prior to contact with the absorbent.

In describing the apparatus of the present invention, which utilizes theaforedescribed process of determining the amount of carbon dioxide inthe anesthesia system,

reference will be made to the accompanying drawings, of which:

FIGURE 1 is a perspective view of the apparatus with the cover brokenaway showing the complete assembly of the same.

FIGURE 2 is a perspective view of the displacement sytem of theapparatus showing control mechanism in relation to the tubulardisplacement circuit.

FIGURE 3 is also a perspective view of the dual gas conditioning unit inrelation to its mounting with sections of the mounting and unit brokenaway to show the interior thereof.

FIGURE 4 is an elevation, partially in section, of one of the cartridgesshowing it mounted in one of the pairs of receivers.

FIGURES 5 through 12 are diagrammatic flow diagrams illustrating thesequential relation of the pump to the control mechanisms and showingthe direction of flow of the gas through the displacement system.

FIGURE 13 is a perspective view of a, modified hydraulic dash-potsystem, which may be utilized in the present device.

The apparatus of the present invention as illustrated in FIGURE 1comprises a base 21, surmounted with mounting plates 22, 23 24, 25, 26and provided with cover 27. Segment gear 28 mounted on shaft 29',journaled on mounting plates 25, 26, is actuated by handle 31 andcooperates with spur gear 32 in energizing spring motor 33 through shaft34. Many types of spring motors may be utilized in the present apparatuswithout departing from the spirit of invention embodied therein,although we have preferentially utilized a spring motor which hassubstantially a constant torque.

Drive Cycle and Regulator Thereof Spring motor 33 mounted on shaft 34,cooperates with one-way clutch 35 to drive meshing gear 36 when cam withthe periphery of the bifurcated pivoted lever 38 by means of tensionspring 51' Pivoted locking lever '52 in its normal position i.e. whenthe machine is at rest or when handle 31 is depressed less than itsmaximum leverage point, is pivoted out of engagemerit with the teeth ofratchet 3t) attached to segment gear 28 and is held out of engagement bymeans of adjustable stop 53 contacting the periphery of arm 37 of thebifurcated pivoted lever 38. When cam lock arm 37 is forced out ofengagement with the. retaining slot of circular cam 39, pivoted lockinglever 52 will pivot on shaft 34 and will engage the teeth of ratchetSfiattached to segment gear 28.

The toothed periphery ofse'gment gear 38 will be prevented from enteringa downward movement due to the contact of locking lever 52 with theteeth of ratchet 30, attached to segment gear 28. The position ofengagement of pivoted locking lever 52 with the teeth of ratchet is suchthat the toothed periphery of ratchet 30 will only be allowed, at thispoint, to move in an upward direction even though a downward torque isapplied to handle 31.

At the end of the driving cycle of segment gear 28, cam lock arm 37 willagain engage circular cam 39 and pivoted locking lever 52, co-actingtherewith, will return to its normal disengaged position.

Drive Speed Control The drive speed of spring motor 33 is controlled byhydraulic dash-pot pump 57 through connecting rod 56 lock arm 37 of thebifurcated pivoted lever 38 is disengaged from the retaining slot ofcircular cam 39-.

The cam lock arm 37 of the bifurcated pivoted lever 38 in its normalposition, i.e., when the machine is at rest or when handle 31 isdepressed less than its maximum leverage point, engages the retainingslot of circular cam 39, and is held in position by tension spring 50.When handle 31 is depressed, pressure bar 41, extending laterally fromthe upper portion of segment gear 28, contacts and depresses relase arm42 of the bifurcated pivoted lever 38 pivoting it on shaft 34 andforcing the cam lock arm 37 out of engagement with the retaining slot ofcircular cam 39, at which time the contact arm 43 of spring loadedpivoted lever 44 will hold cam lock arm 37 out of engagement with theretaining slot of circular cam 39. Gear 36 mounted on shaft 45,journaled on plate 46, rotates cam 47 and cam 48 one cycle, at whichtime pressure bar 49, extending laterally from the lower portion ofsegment gear 28, contacts the release arm 51 of the pivoting pivotedlever 44 on shaft 34 forcing the. contact arm 43 out of engagement withthe cam lock arm 37 allowing the same to return to its normal position.

One-Way Drive Control The function of pivoted locking lever 52 is tocontrol the direction of movement of segment gear 28 to an upwardmovement when cam lock arm 37 is disengaged from the retaining slot ofcircular cam 39 thereby preventing the mechanism from being thrown outof sequence by the accidental recocking of the driving mechanism whilethe same is going through its driving cycle.

Pivoted locking lever 52, journaled on shaft 34, is held in positionwith relation to bifurcated pivoted lever 38, by means of the action ofadjustable stop 53 and spring 54, such that locking lever 52 co-acts inmovement with the bifurcated pivoted lever 38. Adjustable stop 53,mounted on arm 55 of pivoted locking lever 52, is held in contactcleaved to segment gear 28 co-acting with gear 32 to regulate therotation of shaft 34 on which gear 32 is mounted. This inventionincludes in its scope any dashpot pump which would control the speed ofthe spring motor, although we have preferentially utilized a hydraulictype dash-pot pump in the present described embodiment.

The hydraulic dash-pot comprises cylindrical housing block 59 withinwhich is housed cylindrical bore 61 adapted to receive piston 62provided with connecting rod 58. The upper extremital end of housingblock 59 is provided with cover cap 63 through which connecting rod 58operably extends.

The valve control, communicating with cylindrical housing block 59through tube 64, comprises valve housing 65 within which is housedone-way valve 66 and needle valve 67. The function of one-way valve 66is to allow the transfer of hydraulic fluid only from cylindrical bore61 through tube 64 one-way valve 66 tubing 70 into reservoir 68. Thefunction of needle valve 67 is to regulate the rate of flow of hydraulicfluid from reservoir 68 through tube 70 needle valve 67 tube 64 intocylindrical bore 61.

The hydraulic fluid receiver, which is used to store the hydraulicfluid, comprises housing 71 within which is housed reservoir bore 68adapted to receive piston 72 WhlCll rides on the hydraulic fluid andforms an air tight seal for such fluid. Reservoir bore 68 is alsoprovided with capping section 73 through which adjustable rod 74,

- connected to piston 72, also extends.

When handle 31 is depressed, connecting rod 58 is sub ected to an upwardpulling action because its cleave attachment point on arm 69 of segmentgear 28 is raised due to the pivoting of segment gear 28 on shaft 29.The upward torque exerted in connecting rod 58 is in turn communicatedto piston 62, to which said rod is attached, and piston 62 ascends incylindrical bore 61 creating an upward force which drives hydraulicfluid contained in cylindrical bore 61 through tubing 64-, one-way valve66, tubing 70 into reservoir 68.

In driving, energized spring motor 33, in FIGURE 1, rotates shaft 34 andgear 32, mounted thereon, co-acts with segment gear 23 resulting in adownward movement of segment arm 28 due to the pivoting of segment gear23 on shaft 29. When segment gear 28, in FIGURE B, is subjected to adownward movement, piston 62 is forced to descend in cylindrical bore 61by connecting rod 58 which is cleared to segment gear 28. As piston 62is forced to descend in cylindrical bore 61 it creates suction whichdraws fluid from reservoir 68 through tube 79 into the valve controlhousing 65. At this point in the operation, one way valve 66' will beclosed by the force of the flow of the hydraulic fluid, and thehydraulic fluid will be directed to needle valve 67 which will controlthe rate of flow of the hydraulic fluid through tubing 64 again intocylindrical bore 61.

Pump

Mercury displacement pump 75, whose function it is to draw a sample ofthe anesthesia stream into the tubular deplacement system, illustratedin FIGURE 2 and to displace the same through such tubing system, isoscillated on shaft 29 by spring-loaded pivotical lever 76 whosefollower roller 77 rides butterfly cam 48. The shape of the periphery ofbutterfly cam 48 is such that follower roller 77 will impart motion topivoted lever 76 which in turn will pivotally oscillate the mercurydisplacement pump 75 through two cycles of a pendulum movement for everycomplete revolution of butterfly cam 47. The pump 75 may be any one of anumber of con ventional pivoted pumps but we have preferentiallyutilized a mercury piston loaded displacement pump.

The mercury displacement pump 75 comprises a piston housing 73, havinginterconnected dual displacement chambers of equal volume, 79 and 81,pivotally suspended from shaft 29 by arm 80. A volume of mercury iscontained in piston housing 78 and serves as a common piston fordisplacement chambers 79 and 81 and the difference in volume of themercury piston 82 in relation to the sum of the volumes of displacementchambers 79 and 81 is equal to the amount of gas which is desired to bedisplaced through the tubing system which is between about cc. and about50 cc. with the preferential volume being about 20 cc.

When the mercury displacement pump 75 is in its normal position mercurypiston 82 will fill chamber 79 and a void will exist in chamber 81. Aspivoted oscillation is imparted to arm 88, by spring-loaded pivotedlever 75, piston housing 78 will oscillate through a pendulum movementand substantially equal volumes will be displaced in sequence fromchamber 79 and then chamber 81.

In the first one-half cycle of movement of the mercury displacement pump75, piston housing 78 will swing to one side on arm 80 and the mercurypiston will fill the void in chamber 79 resulting in a compression beingcommunicated to the tubing system through tube 83, and simultaneouslywill evacuate chamber 81 creating suc tion which is communicated to thetubing system through tube 84 drawing a sample of the anesthesia gasinto chamber 81.

in the second one-half cycle of movement, piston housing 73 will swingto the opposite side on arm 80 and the mercury piston will fill theevacuation in chamber 81 displacing the gas contained therein throughtube 84 into the tubing system, and simultaneously will evacuate chamber79 creating a suction which is communicated through tube 83 to thetubing system drawing a sample of anesthesia gas from the system throughtube 83 to cham ber 79.

On the third one-half cycle of movement, piston housing 78 will swing tothe same side as in the first onehalf cycle of movement and the mercurypiston will fill the evacuation in chamber 79 displacing the gascontained therein through tube 83- into the tubing system, andsimultaneously will evacuate chamber 81 creating a suction which iscommunicated to the tubing system through tube 84 drawing a sample ofthe anesthesia gas into chamber 81.

The fourth one-half cycle of movement of the mercury displacement pumpis substantially the same as the second one-half cycle of movement.

While motion is being imparted to the mercury displacement pump 75 bymeans of shaft 45 on which cam 47 is mounted, motion is alsosimultaneously being imparted to control bar 85, adapted in housing 86by means of bifurcated pivoted lever 87 riding on cam 48 which is alsomounted on shaft 45.

Mercury Safety Control As is illustrated in FIGURE 1, tube 84-communicating between chamber 81 of the mercury displacement pump 75 andthe tubular displacement system traverses the upper portion of pump arm82, and also tube 83 communicating between chamber 79 and the tubulardisplacement system traverses over the upper portion of pump area 82 inproximity to tube 81. To facilitate an assurance that the mercury inpiston housing 78 will not flow from such housing into the tubulardisplacement system when the machine is raised from its normal position,tubes 83 and 84 are provided with a common pressure bar whose functionit is to cut-oif flow through tubes 83 and 84 when the machine is raisedfrom its position.

The pressure cut-01f bar 142, which perpendicularly traverses over tubes83 and 84 is held in position by spring loaded support bar 143. Supportbar 143 is positioned substantially perpendicular to and extends throughbase 21, and rests on the surface upon which the machine is surmounted,and such bar 143 is held in position by tension spring 144. As themachine is lifted from the surface upon which it is surmounted tensionspring 144 exerts a downward torque and pulls upon support bar 143 sothat a pressure bar 142 pinches tubes 83 and 34 shut thereby preventingthe flow of mercury from either chamber 79 and 81.

Control System Housing 86 provided with control chamber 88, surmountedon base 21 supports the tubular displacement system through which theanesthesia gas is displaced, as illustrated in FIGURE 1 and FIGURE 2.Three flexible sections of this tubular system transverse throughpressure chamber 88, as illustrated in 'FIGURE 2. The first section 89communicates between the four-way intersection 91 and the exhaustpassage 92; the second section 93 communicates between the three-wayintersection 94 and the inlet passage of the humidity control cartridge95, while the third section 96 communicates between the three-wayintersection 94 and the absorbent cartridge 97. The pressure controlsystem comprises control bar 85, journaled between the rocking arms, 98and 99, of the bifurcated pivoted rocking lever 87, which oscillatesthrough an upward and downward movement in pressure chamber 38. Controlbar transverses through pressure chamber 88 and its length is positionedperpendicularly to the length of the three flexible sections which alsotransverse the chamber such that the flexible sections 89 and 93 whichcommunicate with the inlet passage and exhaust pass-ages respectivelyare positioned above the control bar 35 while the flexible section 96'which communicates with the absorbent cartridge 97 is positioned belowsaid control bar. The upward and downward oscillation of control bar 85,which regulates the flow of gas through these aforesaid sections isregulated by pivoted rocking lever 87 whose roller follower 101 ridescam 48. The shape of the periphery of cam 48 is such that followerroller 101 which rides thereon imparts 2 cycles of three positions eachto control bar 85 through pivoted rocking lever 87 for every completerevolution of cam 48. The three poistions imparted to control bar 85correlate either (1) to complete the opening of all of the flexiblesections; (2) to the closing of section 89 which communicates with theexhaust passage 92 and a closing of the inlet passage 93 whichcommunicates with the humidity control cartridge 95, and to thesimultaneous opening of section 96 which communicates with the absorbentcartridge 97; or (3) to 7 the closing of section 96- comrnunicating withthe absorbent cartridge 97 but with a simultaneous closing of section89, which communicates with the exhaust passage 92 and an opening of thepassage 93 which communicates with the humidity control cartridge 95 ofthe gas conditioning unit.

T nbular Alignment Plates The present machine is provided withadjustable alignment plates whose function it is to aid in maintaining asubstantially uniform tubular alignment within pressure chamber 88.Adjustable angle plate 145 is placed in position on the side of housing86 such that one section of it extends into pressure charnber 88 but ispositioned below flexible tubular section 96, and such that anothersection of plate 145 is adjustably mounted on the side of housing 86 asis illustrated in FIGURE 1. Adjustable angle plate 146 is also placed inposition on the side of housing 86 so that one section of itsextendsinto pressure chamber 88 but is positioned above both flexibletubular sections 93 and 89, and so that another section of plate 146 isadjustably mounted on the side of housing 86, as is also illustrated byFIGURE 1.

. Although frequent use causes flexible tubing to exhibit a tendency towarp slightly, the adjustable plates minimize warping effects andsafeguard the accuracy of the machine even though it is subjected tolong and continued use.

Pressure Reading One of the conduits of the four-way intersection 91, asillustrated in FIGURE 2, is provided with a vacuum gauge of theMagnehelic type whose function it is to indicate the pressure change dueto the extractions of carbon dioxide from a sample being displacedthrough the tubular displacement system. Any one of a number of deviceswhich measure low vacuum changes may be utilized in the presentinvention but we have preferentially utilized a Magnehelic type gauge inthe present embodiment which is calibrated to indicate the change inpressure in related percent carbon dioxide extracted from the displacedsample.

Handle Positioning There exists an area of clearance, between thefingers of interlocking grip 1G4 and the fingers of interlocking grip105, of such a magnitude that handle 21 is allowed to be moved to aposition so that it is perpendicular to the horizontal base of themachine and in which position the machine may normally be carriedwithout encountering any inherent damage to the mechanism.

Valve Release Interlocking grip 104, fused to handle 31, engagesinterlocking grip 105 when handle 31 is depressed to its maximumleverage point. Index control 1116, attached to interlocking grip 105,is in the shape of a segment whose periphery containsa slot whichreceives a spring-loaded stop 107 when handle 31 is in positionperpendicular to the horizontal base of the machine. When handle 31 ismoved from its perpendicular inactivated position to its maximumleverage point, spring-loaded stop 107 is depressed by the movement ofthe periphery of index control 106 and in such depressed positiontravels over the periphery of said index control during its movement.

Adjustable pressure bar 113% extends laterally from the upper portion.of index control 106 and contacts slotted indexing plate 102 resultingin control bar 85 being moved to a neutral position in control chamber88 when handle 31 is moved to a position perpendicular to the horizontalbase of the machine. When control bar 85 is in a neutral position incontrol chamber 88 the'three flexible tubes transversing control chamber88 will not be pinched shut. The function of indexing plate 182 is toindex control bar 85 to a neutral position thereby aiding infacilitating the relief of pressure in the tubular system and to preventtrol bar is allowed to be oscillated in an upward and downward movementby the action (aforedescribed) of pivoted rocking lever 87. After themachine has progressed through its driving cycle, handle 31 may be againmoved to its perpendicular position at which point indexing plate 102will bring pressure bar 103 to a neutral position in control chamber 88.

. Conditioning Assembly The gas conditioning assembly, illustrated inFIGURES 2 and 3, comprises amount housing 109 provided with four-springloaded receivers 111, 112, 113, 114, whose function it is to retain thegas conditioning units and 97 in a substantially air-tight position inrelation to the displacement circuit of the present apparatus when theseunits are surmounted on housing 109. Each of the receivers,.for example111 illustrated in FIGURE 4, contains a passage-like conduit, forexample 115, which communicates with the gas displacement system. Theconduit 115 in receiver 111 communicates with the inlet passage 93transversing the control chamber 88 while the conduit 116 in receiver113 communicates with the rebreathing system (not shown). Also theconduit 117 in receiver 112 communicates with the four-way intersection91 and the conduit 118 in receiver 114 communicates with the passagewhich transverses the control chamber and it is connected to thethree-way intersection.

Conditioning Unit The gas conditioning units 95 and 97 respectivelyhouse the humidifying agent and the absorbent agent utilized in thepresent apparatus and these units may be constructed from glass,polyethylene or any one of a number of plastic type materials which arenot susceptible to reaction with caustic materials. One of the functionsof these units is to preventatmospheric contamination of the chargescontained therein. Units 95 and 97 may be any one of a number of hollowhousings, which would perform the aforesaid function. These may be ofeither closed end construction or in the alternative open endconstruction provided-with end sealing members, as long as theextremital ends of said units are adapted to fit operatively into the.spring-loaded receivers mounted on housing 109.

One end of each cartridge has the shape of a cone and is sealed by anapex section which is to be broken off before use. The opposite ends areclosed by caps 121 (FIG. 4) which also terminate in conical endportions, the sealed tips of which are to be removed before use.

The function of cartridge 95 is to house the humidity control charge andit is adapted to receive a charge volume between about 10 cc. and about20 cc. with the preferential charge volume being about 10 cc. A volumesubstantially less than about 10 cc. would be unreliable in humidifyingthe gas displacement sample with which the charge is contacted whereas acharge volume greater than about 20 cc. would be impossible to purge.The function of the humidifying charge is to adjust the moisture contentof the gas, with which it is contacted, to equilib rium with themoisture in the absorbent charge contained in cartridge 97. Thehumidifying agent preferentially utilized as charge is moist ammoniumsulfate.

The function of cartridge 97 is to house the absorbent charge and it isadapted to receive a charge volume between about 5 grams and about 30grams with the preferential charge volume being about 10 grams. Thefunction of the absorbent charge is to substantially extract the carbondioxide from any of the anesthesia gas to which it is contacted. Acharge volume of less than about grams of soda lime would present toosmall a surface for absorptive utility in the present apparatus andhence would be unreliable in analytically extracting the carbon dioxidefrom the gas displacement sample whereas a volume greater than about 30grams would be ineffectively purged. The charge volume of about gramswould provide 100 analyses averaging about 5% in carbon dioxide with asafety margin of about 50 analyses before the accuracy of the apparatusis affected significantly.

In practice the cartridges may be stored prior to use and the effectivereaction capacity of their respective charges will not be altered. Whenthe cartridges are to be used, the anesthetist merely breaks off theapex at each end of each cartridge and mounts the pair of cartridges inthe receivers on housing 109. The cone apexes and the closed ends may beeasily removed by applying a slight pressure thereto with an appropriateimplement, for instance a knife. When the cone apex is removed from itscartridge an apex orifice, which communicates with the charge in thecartridge, is opened which is substantially of the same area as the baseof the removed cone apex.

Spring-loaded receivers 113 and 111 respectively are adapted to receivethe apex orifice 131 and the hollow tubular member 128 of humidifyingcartridge 95 when such cartridge is mounted on housing 109. Alsospringloaded receivers 114 and 112 respectively are adapted to receivethe apex orifice 129 and the hollow tubular member 122. of the absorbentcartridge 97 when such cartridge is mounted on housing 109. The dualunit is illustrated in FIGURE 3. The outer convex surface area of theunits, i.e. cartridges 95 and 97, are interconnected by a key-holedspacing segment 127. The function of the spacing segment 127 is to aligncartridges 95 and 97 in relation to each other so that when the dualunit is surmounted on housing 199 orifices 129 and 131 will operativelyfit respectively into receivers 114- and 113 and hollow tubular members:122 and 1-28 will operatively fit respectively into receivers 112 and111 since the keyhole 100 must fit over pin 110, reversal of thecartridges is impossible.

The gas conditioning units of the present apparatus are not only novelbut are very practical for use in conjunction with the present apparatusand are comparatively easy to fabricate by conventional process such asmolding or extrusion. The cartridges are very easy to mount on thepresent apparatus and replacement is comparatively simple. For ease ofoperation and convenience the anesthesiologist does not have to replacethe cartridges individually but may mount or replace these cartridges asa dual unit. The unit may be changed after a periodic lapse of time orafter the machine has cycled through its operation a set number of timesas indicated by a meter, such as meter 132, illustrated in FIGURE 1,which is actuated by shaft 45 through meter arm 134. Theanesthesiologist may always feel certain that the gas sample is properlyconditioned as it flows through the displacement system if effectiveconditioning charges are mounted in the circuit. If any doubt exists asto the efiiciency of the operation the unit should be replacedimmediately.

F low Diagram The operation of the present apparatus will best beillustrated by reference to the flow diagrams as shown in FIGURES 5through 12. The flow diagrams illustrate the action of the sequentialmovements of the mercury displacement pump 75 and of the control bar 85on the tubular gas displacement system. For the sake of clarity, theconduit 93, as shown in FIGURE 5, which perpendicularly transverses overcontrol bar 85 and which communicates between the humidity cartridge 95and displacement chamber 7 9 of the mercury displacement pump 75, ishereinafter referred to as the inlet passage 93. Conduit 89 whichperpendicularly transverses over con trol bar 85 and communicatesbetween the atmosphere and displacement chamber 81 of the mercurydisplacement pump 50 is hereinafter referred to as the exhaust passage89. Conduit 96 which perpendicularly transverses under control bar andcommunicates between inle-t passage 93 on the pump side of control bar85 and the exhaust passage 104 on the pump side of control bar 85 ishereinafter referred to as absorbent line 98 because the absorbentcartridge 97 is positioned in this conduit.

When the apparatus is in its normal position as illustrated in FIGURE 5,i.e., when the machine is at rest or when handle 31 is depressed lessthan its maximum leverage point, control bar 85, hereinbefore describedwill be neutrally positioned and the inlet passage 93, the exhaustpassage 89, and the absorbent line 98 will be opened.

Operation When the anesthesiologist desires to be appraised of theamount of carbon dioxide in the rebreathing system he merely forceshandle 31 down to its maximum leverage point and releases it, at whichtime energized spring motor 33 will drive gear 36 by one-way clutch 35imparting a two cycle movement of two positions each to mercurydisplacement pump 75 through pivot lever 76 whose follower roller 77rides cam 48 which is rotated on shaft 45, and simultaneously impartinga two cycle movement of three positions each to control bar 85, inpressure chamber 88, whose follower roller 191 rides cam 47 which isalso rotated on shaft 45.

In the first one-half cycle movement, control bar 8 5 by its action,hereinbefore described, will close the absorbent line 98 and allow theintake passage 93 and the exhaust passage 39 to open, as illustrated inFIGURE 6. Sequentially the mercury pump 75 will then tilt and mercurypiston 82 will fill the void in displacement chamber 81 and willsimultaneously evacuate displacement chamber 79 thereby drawing a sampleof the anesthesia gas stream from the close circuit rebreathing system(not shown) into humidity cartridge through intake passage 93 intodisplacement chamber 79 as is also illustrated in FIGURE 6. At thispoint the relative humidity of the gas in the displacement system isstandardized due to its contact with the humidifying agent contained incartridge 95.

While the pump is held in the aforesaid position, as illustrated inFIGURE 7, the next sequential movement of control bar 85 will allow theabsorbent line 98, the intake passage 83 and the exhaust passage 89 allto open momentarily thereby equalizing the system to atmosphericpressure. At this point the gas in the displacement system issubstantially at atmospheric pressure.

In the neXt one-half cycle of movement, control bar 85, by its actionwill close intake passage 93 and exhaust passage 89 and allow theabsorbent line 96 to open, sequentially the mercury pump 75 will thentilt to a new position so that mercury piston 82, by its action willfill the gas filled space in displacement chamber 79, displacing the gasback through the intake passage 93 into the absorbent line 98 andsimultaneously displacement chamber 81 will become evacuated therebydrawing the displaced gas in the absorbent line 98 through the absorbentcartridge 97 into the displacement chamber 81 as illustrated in FIGURE8. At this point the gas displaced through the absorbent cartridge 97has had its carbon dioxide content substantially extracted.

While the pump is held in the aforesaid position, as illustrated inFIGURE 9, control bar 85 by its action will open the intake passage 93and exhaust passage 89 and close the absorbent line 98.

In the third one-half cycle of movement, the mercury pump 75 will againtilt and the mercury piston 82, by its action will again fill thegas-filled space in displacement chamber 81, displacing the gas throughthe exhaust passage 89 to the atmosphere and simultaneously displacementchamber 79 will become evacuated thereby drawing a new sample from theanesthesia gas stream through the intake passage 93 to chamber 79 asillustrated in FIGURE it). At this point the system hasbeensubstantially purged andthe apparatus has started its analyticalcycle. Also the new sample of gas drawn into the displacement system hashad its relative humidity standardized by being contacted with thehumidity agent in cartridge 95.

While the pump is held in the aforesaid position, as illustrated inFIGURE 11, the next sequential movement of control bar 85 will allow theabsorbent line 98, the intake passage 93, and the exhaust passage 89 allto open momentarily thereby equalizing the system to atmosphericpressure. At this point the gas in the displacement system issubstantially at atmospheric pressure.

In the next one-half cycle of movement, as illustrated in FIGURE 12, thenext sequential movement of control bar 85 by its action will allow theabsorbent line 98 to remain open but will close the intake passage 93and exhaust passage 89, sequentially the mercury pump 75 will then tiltto a new position so that mercury piston 82 by its action will fill thegas-filled space in displacement chamber 79 displacing the gas backthrough the intake passage 93 into the absorbent line 98 andsimultaneously displacement chamber 81 will become evacuated therebydrawing the displaced gas in the absorbent line 98 through the absorbentcartridge 97 into the displacement chamber 81. At this point the gasdisplaced through the absorbent cartridge 97 has had its carbon dioxidecontent substantially extracted and a pressure change is produced bysuch extraction which is proportional to the carbon dioxide content ofthe gas. The apparatus has completed its mechanical operation and theanesthesiologist may be quickly appraised of the amount of carbondioxide in the system by a vacuum gauge directly connected to exhaustline 89 between the control bar 85 and the displacement chamber 81, asillustrated in FIGURE 12.

The present apparatus is automatically purged during the first fullcycle of its operation. This purge cycle is utilized to remove any ofthe gas remaining in the system from a previous analysis therebyavoiding contamination of the sample upon which the final determinationof carbon dioxide will be made.

The reading on the gauge is directly related to the carbon dioxideextracted from the displaced gas sample. This pressure reading issubstantially unaffected by a pressure differential due to the exchangeof moisture between the sample and the absorbent because the moisturecontent of the sample has been standardized prior to contact with theabsorbent by passing the sample through the humidity cartridge 95. Thisstandardization adjusts the moisture content of the sample to the amountof moisture which is in equilibrium with the absorbent and thereforewhen said sample is contacted with the absorbent substantially nomoisture exchange will take place therebetween.

It will be apparent to those versed in the art that many modificationsmay be incorporated into the present invention without departing fromthe spirit of invention embodied therein.

In illustration, FIGURE 13 sets forth a hyd-aulic dashpot system whichmay be utilized in place of the present system. This hydraulic dash-potcomprises cylindrical housing block 132, within which is housed cylndrical bore 133 adapted to receive double action piston 134 providedwith connecting rods 135 and 136. The extremital ends of housing block132 are provided with coupling caps 137 and'138 through which connectingrods 135 and 136 respectively extend.

The valve control of this system is attached to coupling cap 137 andcomprises valve housing 139 within which is'housed one-way valve 141 andneedle valve 142. The

function of one-way valve 141 is to allow the transfer of hydraulicfluid only from cylindrical bore 133 through valve housing 139 to tubing143 back to cylindrical bore 133 through coupling 138. The function ofneedle valve 142 is to regulate the rate of flow of hydraulic fluid fromcylindrical bore 133, through tubing 143, valve control 12 housing 139,and into cylindrical bore 133 by way of coupling 1317f When handle 31 isdepressed, connecting rod 135 is subjected to an upward pulling actionbecause its cleave attachment point on arm 69 of segment gear 28 israised due to the pivotingof segment gear 28 on shaft 29. The upwardtorque exerted on connecting rod 135 is in turn communicated to piston134, to which said rod is attached, and piston 134 will ascend incylindrical bore 133 creating an upward force which drives hydraulicfluid through coupling cap 137 into and by one way valve 141 and thencethrough tubing 1143 again into cylindrical bore 133 by way of couplingcap 133. The driving upward force created in the upper section ofcylindrical bore 133 is also aided by a suction force created in thelower section of cylindrical bore 133 by the ascent of piston 134therein.

In driving, energized spring motor 33, in FIGURE 1, rotates shaft 34.Gear 22, mounted on shaft 34, co acts with segment gear 28 resulting ina downward movement of arm 69 due to the pivoting of segment gear 28 inshaft 29. When segment gear 23, in FIGURE 12, is subjected to a downwardmovement, piston 134 is forced to descend in cylindrical bore 133 byconnecting rod 135 which is cleaved to segment gear 28. As piston 134 isforced to descend in cylindrical bore 133 it communicates a downwardtorque to the hydraulic fluid contained therein and the fluid is forcedthrough coupling 138 into tubing 143 and into valve control housing 139.

At this point in the operation, one-way valve 141 will be closed by theforce of the flow of the hydraulic fluid, and the hydraulic fluid willbe directed through needle valve 142 which will control its rate of flowinto cylindrical bore 133 by way of coupling 138.

A further modification which is applicable to the cartridges and 97 liesin the fact that the cone apexes 121, and closed ends of 124, 126 do nothave to be adapted with a circumferential groove. The function of thisgroove is to aid in the respective removal of the apexes and closed endsof such cartridges, however it has been found that such cartridges maybe produced from plastic material by conventional processes in such amanner that the respective apexcs and cones of such cartridges may beeasily snipped off by an ordinary cutting edge without the utilizationof a circumferential groove.

This application is a divisional application of our copendingapplication, Serial No. 772,910, filed November 10, 1958, now Patent No.3,035,903, dated May 22, 1962.

We claim:

1. In the apparatus for determining the amount of carbon dioxide in asample of an anesthetic gas stream, said apparatus having humidifyingmeans for standardizing the relative humidity of said sample, absorbentmeans for absorbing the carbon dioxide from said sample so standardizedin humidity, means for observing the change in the amount of said sampleas the result of the removal of said carbon dioxide, and passagewaysadapted to transfer and control the flow of said sample through theabove three means; the improvement thereof comprising, in combination: areplaceable humidifying cartridge as said humidifying means, areplaceable absorption cartridge as said absorption means, and a housingadapted to receive said cartridges and toprovide for the passage of gastherethrough; each of said cartridges comprising a hollow,noncollapsible tubular body with conical end openings at both endsproviding communication with the interior of said tubular body, saidhousing comprising a supporting member carrying four spring-loadedreceivers in verticallypaired relationship, each pair of receivers beingadapted to receive one of said cartridges and to close thereover, andeach of said receivers having a conduit communicating with saidpassageways and adapted to register with one of said openings in agas-tight manner, the pair of cartridges being joined by a spacingsegment to maintain the carfridges in spaced, parallel relationshipcorresponding to the position of said receivers, said segment having an13 aperture adapted to register with otherwise interfering meansassociated with the housing, Where-by placing the cartridges inincorrect gas circuits in said apparatus is made impossible.

2. A replaceable cartridge for retaining particulate gas treating agentsin an anesthetic gas-analyzing apparatus comprising a pair of closed,non-collapsible, tubular bodies maintained in parallel, spacedrelationship by a spacing segment fastened to each body and extendingbetween them, an off-center keyhole aperture formed in the spacingsegment, each end of each body being closed by a coaxially taperedsection having a sealed, severabie tip, said sections when said tips areremoved providing a fluid communication with the interior of said bodyand being adapted to form a gas-tight fit with two complementary,vertically-spaced, spring-loaded receivers, having conduits whichregister with the terminal exterior surfaces of said sections, theposition of the keyhole in the spacing segment being such as to registerwith a cooperating off-center pin associated with the receivers topermit the insertion of the cartridge only in the correct gas circuitsof the apparatus.

References Cited in the file of this patent UNITED STATES PATENTS1,452,801 Goodchild Apr. 24, 1923 2,099,412 Seidler Nov. 16, 19372,166,307 Libby July 18, 1939 2,176,462 McAllister Oct. 17, 19392,448,206 Bailey Aug. 31, 1948 2,489,654 Main-Smith et a1 Nov. 29, 19492,591,691 Forrester Apr. 8, 1952 2,750,068 Platt June 12, 1956 2,819,723Meyer Jan. 14, 1.958 2,893,611 Akers July 7, 1959 FOREIGN PATENTS 73,644France Sept. 5, 1960 (Addition)

1. IN THE APPARATUS FOR DETERMINING THE AMOUNT OF CAR BON DIOXIDE IN ASAMPLE OF AN ANESTHETIC GAS STREAM, SAID APPARATUS HAVING HUMIDIFYINGMEANS FOR STANDARDIZING THE RELATIVE HUMIDITY OF SAID SAMPLE, ABSORBENTMEANS FOR ABSORBING THE CARBON DIOXIDE FROM SAID SAMPLE SO STAND ARDIZEDIN HUMIDITY, MEANS FOR OBSERVING THE CHANGE IN THE AMOUNT OF SAID SAMPLEAS THE RESULT OF THE REMOVAL OF SAID CARBON DIOXIDE, AND PASSAGEWAYSADAPTED TO TRANSFER AND CONTROL THE FLOW OF SAID SAMPLE THROUGH THEABOVE THREE MEANS; THE IMPROVEMENT THEREOF COMPRISING, IN COMBINTATION:A REPLACEABLE HUMIDIFYING CARTRIDGE AS SAID HUMIDIFYING MEANS, AREPLACEABLE ABSORPTION CARTRIDGE AS SAID ABSORPTION MEANS, AND A HOUSINGADAPTED TO RECEIVE SAID CARTRIDGES AND TO PROVIDE FOR THE PASSAGE OF GASTHERETHROUGH; EACH OF SAID CARTRIDGES COMPRISING A HOLLOW,NONCOLLAPSIBLE TUBULAR BODY WITH CONICAL END OPENINGS AT BOTH